In a manufacture process of a semiconductor apparatus, there is a need to transfer a substrate such as a semiconductor wafer or the like between chambers having pressure atmospheres with different vacuum degrees. The transferring of the substrate is performed through substrate transferring ports provided in sidewalls of the chambers after pressure is adjusted so as to reduce a difference in pressure among the respective chambers. In order to hermetically seal the substrate transferring ports before and after the transferring of the substrate, a gate valve unit is provided between the chambers (see, for example, Patent Document 1).
Patent Document 1 discloses a gate valve unit provided between a process chamber for performing a substrate processing process and a transfer chamber for transferring a substrate. In the gate valve, one sealing member is provided between each chamber and the gate valve unit to surround a substrate transferring port so that the substrate transferring port can be hermetically sealed to prevent air from entering.
However, since the sealing member provided in the gate valve unit is composed of, e.g., an O-ring made of fluorine-based resin, a sealing function is deteriorated when the sealing member is heated, which allows air to penetrate. Particularly, in case of a hot wall chamber, a sidewall of the chamber is heated which performing film formation processing or annealing by heating the substrate within the process chamber. In that case, since the heat of the sidewall is transmitted to the gate valve unit, even the sealing member of the transfer chamber as well as the sealing member of the process chamber is heated, which deteriorates the sealing function.
Like this, if the sealing member allows air to penetrate, the air enters the interior of the chamber through the substrate transferring port to increase pressure in the chamber, which causes such a problem that a target degree of vacuum cannot be maintained. In this case, when a vacuum degree of the chamber is low (when pressure in the chamber is high), a variation in pressure may be ignored, but at pressure lower than, e.g., a 10−6 Torr order, as the vacuum degree increases (as the pressure is lowered), an amount of the air that penetrates through the sealing member increases, and a variation in pressure in the chamber may not be ignored. Furthermore, when a temperature of the O-ring heated at pressure lower than a 10−7 Torr order exceeds room temperature, the pressure in the chamber may not be maintained even at a relatively low temperature equal to or less than 100° C.
Meanwhile, Patent Document 2 discloses a sealing structure applied to an airtight processing container for introducing corrosive gas and a cover capable of opening and closing the container, wherein the sealing structure is configured to be double sealed with a first sealing member covered by a metal surface and an outer second sealing member composed of an O-ring made of a rubber material because when only one sealing member is used, it may be easily deteriorated due to the corrosive gas, and a communication hole for communicating a gap between the sealing members with the interior of the processing container is provided, thereby reducing the deterioration of the sealing members.
However, since the double sealing members disclosed in Patent Document 2, which are applied to one airtight processing container (process chamber) and the cover, are different from a gate valve unit provided between two chambers as disclosed in Patent Document 1 with respect to the configuration and condition thereof, the double sealing members may be completely applied to a process chamber. Although the double sealing members are applied to the process chamber, a sealing function thereof is deteriorated, thereby still failing to prevent air from entering the interior of a transfer chamber. Furthermore, the communicate hole provided between the first and second sealing members is intended to prevent the deterioration of the first and second sealing members resulting from the entry of corrosive gas into the gap between the first and second sealing members by maintaining pressure in the gap between the first and second sealing members to be equal to that in the processing container, but is not intended to maintain the pressure of the container itself.
[Patent Document 1] Japanese Patent Application Publication No. 2001-324032
[Patent Document 2] Japanese Patent Application Publication No. H06-247460